1. Field of the Invention
The present invention relates to paper-making machines and, more particularly, to the measurement of web thickness in a paper-making machine.
2. Description of the Related Art
The problems associated with the production of a web of a fiber material such as paper having a consistent thickness (or consistency or height) along the machine-direction (MD) and the cross-direction (CD) thereof, are well known in the art. Various production factors affect web thickness. Most if not all of the various production factors are controllable given relevant and accurate information about the web at a point or points along its production path. Maintaining a consistent profile is essential for the final product.
Also, it is necessary to determine that the web maintains a consistent profile. While there are seemingly many locations to determine the profile of the web, the type of system for making that determination generally dictates where the profiling system must be placed. In some cases more that one position along the web is necessary. It is known to perform weight profiling on the web (paper) in order to determine MD and CD consistency where this information is used to provide some control of the production variables. This category includes visual monitoring of the dry line, and use of ultrasonics at the wet end for determining wet sheet thickness in the MD sense. Devices as described above are generally located under the sensors that obtain MD and CD data for consistency determination at the wet end of a paper-making machine.
What is needed in the art is a wet end or dry end thickness consistency measurement apparatus and/or method.